The present invention generally relates to improving the mixing efficiency of an additive in a liquid flowing under pressure through a large diameter conduit. The present invention more particularly relates to mixing systems in which a side stream is diverted from the main liquid flow, an additive mixed with the side stream, and the concentrated mixture injected back into the large diameter conduit.
The present invention is applicable to treatment of liquids by the infusion of additives. While the structural components of the invention may be utilized for treating many kinds of liquids, its principal application will be in the field of water treatment where there is substantial volumetric flow. For example, embodiments of the present invention may be utilized in municipal waste water treatment facilities where flow rates are at least 500 gallons per minute, and generally much higher. In such systems, it is desired to achieve effective and efficient blending of the returning side stream into the main flow of liquid. The volumes of water requiring treatment are typically substantial, and reducing or eliminating the amount of time required for any storage of the liquid is desirable. Thus treating the water as it is flowing—as opposed to processes employing settling ponds and/or holding tanks—can be advantageous in expediting the treatment process and reducing capital expenditures by reducing the required storage capacity of the overall system. These dynamic mixing systems provide even more advantage when the volume of the side stream can be reduced because of the corresponding reduction in energy required for processing the side stream and infusing the side stream back into the main flow of liquid.
The treatment substances utilized with the present invention may be in the form of a gas, liquid or slurry, where the treatment substance is capable of being mixed with the side stream through a mixing apparatus, such as a venturi mixing injector, chemical mixer, mixing nozzle. One well-known example of a treatment substance is ozone which is a very effective disinfectant chemical which is in gas form which decomposes into molecular oxygen at standard temperature and pressure. As described in U.S. Pat. No. 7,779,864, in which one of the inventors herein is named as an inventor, ozone may be mixed with the mixing apparatus into the side stream and then infused through nozzles into a large diameter conduit into a mainstream of flowing liquid. The conduit is a large pipe often on the order of 48 inches in diameter.
The object of present invention is to improve the transfer efficiency of the treatment substance into the flowing stream. Improvements in transfer efficiency will result in reduction of the treatment time required for the flowing stream, which can minimize retaining the water for additional treatment and prevents “over-dosing” the stream in order to be assured of a sufficiency throughout the treated liquid. In other words, improving the mass transfer efficiency may reduce initial capital investment in the system and reduce the operating expense for the system.